Pneumatic roller compactor



Spt; 16, 1952 c. w. BROS ETAL 2,610,557

' PNEUMATIC ROLLER COMPACTOR Filed Nov. 17, 1949 5 Sheets-Sheet 1 FILE 1 CHESTER n4 BR05- I E flkawe O. ll mulwsmv Mars: .0. GII/G-A/lh? Sept. 1952 c. w. BROS ETAL 2,610,557

PNEUMATIC ROLLER COMPACTOR Filed Nov. 17, 1949 s Sheets-Sheet CHESTER H4 BRos ARCH/E a MAL/44180 (/4yss 0. Gale/YARD Patented Sept. 16, 1952 PNEUMATIC ROLLER CQMPACTGR Chester W. Bros, Archie o. Williamson, and Ulyss O. Guignard, Minneapolis, Minn, assignors to Wm. Bros. Boiler and Manufacturing Company,

Minneapolis, Minn, a corporation of Minnesota Application November 17, 1949, No. 127,865

This invention relates to the art of compact= Y ing earth for roads, highways, airport runways,

fills for dams, etc. where deep'penetration and uniform but maximum density are important objectives, and the primary purpose is to provide a novel, eflicient and practical pneumatic tired compactor that will effectively yet economically meet these rigid objectives or requirements.

Soil stabilization and compaction problems are not new and. have been efficiently solved in many instances andby various means. But with increaseddemands resultingfrom modern heavy traffic and load conditions the problem becomes more acute and critical, because unless the foundation soil structures are compacted or compressedby equipment at least as heavy as that which is to subsequently travel thereover there will be additional and irregular compaction and consolidation that will injuriously disrupt the surface condition that was prepared for such subsequent trafiic.

A typical exigency is that represented by airport runways which must receive and support aircraft weighing as much as three hundred thousand pounds. The impact thus resulting, in effect, from wheel-loads of one hundred fifty thousand pounds is such as to break down the runway pavement unless it is properly supported by base courses and subgrades that have been compacted to an extremely high degree of density and to a depth of as much as five to six feet below the surface.

The advantages resulting from the use of pneumatic tired compaction rollers have been recognized for some time. They produce a kneading and densification action, irrespective of ground surface irregularities, that is far superior to that obtained by hard steel rollers, regardless of size or weight.

It is also, evident that the depth of pressure penetration and the degree of subgrade density will be increased by using larger tires and imposing heavier loads. It is found, however, that the problem cannot be solved by merely increasing size and weight of existing rollers because a number of practical andoperational considerations intervene. These include, body rigidity, transport, maneuverability, cost, available tire and tractor power limitations, safety, weight'concentration, and other important factors.

. To obtain the required depth and density coma relatively limited ground surface area,-to prevent dissipation or lateral dispersion of the vertical pressures, and must also be uniformly, distributed at all times to be supporting wheels so that no one of them will be subjected to weight pressure beyond which its pneumatic tire will support without blowing out. These tires must necessarily be of giant size, represent a very substantial investment, and their replacement or repair is accordingly an important item in the construction and maintenance costof this equipment.

With the foregoing and other practical problems and technical difficulties in mind, we have developed and perfected a pneumatic tired compactor which has been thoroughly tested and found extremely practical and efficient in actual use. This machine is exemplified in the accompanying drawings, wherein- Fig. 1 is a side elevation of a preferred form of our compactor showing it directly connected to a tractor.

Fig. 2 is an enlarged sectional plan view on the line 2-2 in Fig. 1.

Fig. 3 is a cross sectional elevation on the line 3-3 in Fig. 2.

Fig. 4 is an elevation, partly in cross section, showing the body and wheels in tilted positions as when travelling over an irregular surface.

Fig. 5 shows a modified form of machine in this instance the main body having a forward goose-neck draft structure for mounting on a dolly which is in turn connected to the pulling tractor.

Fig. 6 is a plan view'of the structure shown in Fig. 5.

Referring to the drawings more particularly and by reference characters A (Figs. 1-4) designates a large steel box which forms the main body structure of the machine. I This box is substantially rectangular, in plan, but in side elevation has an arched, transversely extended recess for the reception of the supporting wheelsB, C, D and E. This resultsin deep wells, at fore and aft ends of the box; and the distribution of weight including ballast loaded into the box, is such that the center of gravity is directly over or slightly forward of the wheel axis so as to impose maximum load pressure on the tires.

When the'niachine is in operation it is loaded with ballast, such as wet sand, until the total weight approximates or exceeds thirty-five tons, with a result that the box is subjected to very great torsional and twisting stresses, particularly when moving over irregularterrain. To counteract these stresses and to providea maxi- 3 mum degree of body rigidity and design and construction of the body proper becomes an important problem.

In the structure illustrated in Figs. 1-4, the body box is made up of heavy steel plate side, end and bottom walls I, 8 and 9, respectively, all securely welded together, and a similarly secured arched bottom plate it], over the wheels.

A draft beam ll extends centrally and longitudinally through the entire length of the bottom of the box and forwardly therebeyond (Fig. l) to a universal coupling l2 that connects it to the drawbar I3 of the tractor F. This draft beam may be of any substantial steel. deslgn. but. is

preferably narrow in width, and in the-present;

instance comprises a center plate! sand arpair :of transversely curved or concaved side. plates 15, all welded into a single rigid unit. This beam is also rigidly secured, preferably by welding, to the end walls 8, to the bottom wall 9, and to the vertical lower portions of the arched bottom plate 55. It will be seen that it connects these portions E!) (Fig. 2) by extending across the wheel recess, between the wheelsC and D, so as. to transmit the draft force directly to the rearof the box, but is sufficiently narrow, and in the transverse horizontal plane of the wheelaxes, so as to permit the wheels C and D-to be closely spaced with respect toeach other- This position of the center beam is also such as to not interfere with the wheel unit oscillations as will presently beset forth. 7 7

It will also be noted that the upper.- arched portion of the plate lilis reinforced-by a generally semi-circular plate 16 which may be an integral extension of the beaml lwhich extends-forwardly beyond the box A'is further rigidly connected to the forward wall 8..by-a;center.gusset plate H and upwardly and outwardlyniagonall-yextended brace bars I8. 7

In the modification shown in Figs. and 6,- the box Al, is substantially similar to the boxxA, except that the beam l I does notextend directly forwardly to the draft vehicle. In this instance the roller has a generally goose-necked :draft connection in the form of a hollowsbeam l 9, which is triangular .in plan-and-extends forwardly from the upper part of the box A l. Thlsbeamis then connected to the draft beam. by an inclined beam '26, and terminates in a-casting 2| pivotally mounted on a two-wheeled doll-y 22. Thedolly thus forms an independent support for the-roller and is merely connected to the tractor by a .conventional draft tongue 23.

Returning now to the more critical wheel and tire construction, arrangement and function, it will be seen thatthe wheels are. arrlangeddn coaxially aligned pairs, the wheels of each pairbeing mounted on opposite ends of a shaft2-4 the middle of which extends through and l'srigldly secured in a fore-and-aft extending beam 25. The ends of the beams are-oscillatably mounted in opposed bearings 25 intransversely extending bearing beams 26 rig-idlysecuredto 'thelower ends of the recess wall it. Thebeams i'fi irrad'dition to mounting the shafts-2d operatetomai-ntain parallelism between the lower ends of the recess wall I e, retainproper-spacingxbetween said lower ends and cooperate with the fore-and-aft supports to provide a reinforcement forthe wall of the arched recess. It willathns be'ev-ident that the totalweight of theloaded box will be equally imposed, transversely; uponthe two beams '25, asthey are .equally spaced from the transverse center of the machine, andthat theloadimposed 4 on each beam will be equally distributed to the two wheels mounted on it, as the wheels are free to oscillate or rock in a transverse vertical plane about the bearing centers of each beam. In short, if the gross weight of the machine is fifty tons (as in the tested pilot model) the ground pressure exerted by each tire will remain constant at approximately twelve and one-half tons per tire irrespective of anticipated ground contour irregularities. t will also be evident that since the wheels are disposed in a line substantially under the center (longitudinally) of load gravity, the groundsurface pressure will be much more concent-rated than if the load were carried between A a single wheel series machine, it is recognized that the great weight required must not only be concentrated in a single transverse strip and equally distributed to the four wheels, but also that the wheels. must ,be very .close together in ordertobest utilize the combined down pressures and prevent the vertical compaction movement from escapin in the form of upward squeezing ofsoil between the. wheels.

Our wheel mounting is such thatthe transverse space betweenthe tires .of each pair needbe very little greater, than the. thickness .of. the .oscillating lor. rocking beam .25 and thespace between the tires Cand D canbe as narrow as .the spaces between tires B- -.C .orDeeE. .The effectiveness of this arrangement, is illustrated in Fig. 3, where diverging dcttedlines 27 indicated how the lateral dispersion cfvertlcal pressures are coordinated so that the actual result is virtually the same as if the tires were immediately adjacent .to each other, the intervening spacesbeing much too narrow to permit the upward escape of any appreciable compaction pressures. To the bestv of our knowledge noone has previously designed a machine that will thus concentrate compaction pressures while also equally distributing the weight to wheels that will accommodate themselves to irregular terrain. In this connectionit :may be noted that since the tires employedareof unusually largedimensions (outer-diameter of five feet or over) the wheel axles cannot be mounted in vertically depending brackets if the wheels are to have both ierequired proximity and freedom'for oscillation, as such brackets would interfere with such relationship and action. -As the wheels are independently rotatable the entire machine can be turned'in short radius, and the large tire diameters also insure that even soft ground will be rolled down-and not pushed in a wave in advance of the wheels. .Our experience indicates that within practicable size limits a machine embodying this invention is I required to ltiave not more nor less than four compaction ires.

Itis understood that suitable changesormodificationsmay be made in the design/and details of constructionas herein-disclosed, provided such changes or modifications com-e withinthe spirit andscope of the. appended claims. Having now therefore fully illustrated and described the preferred embodiments of our invention what are claim to .beqnew and desire to. protect: by Letters Patent is. r I V 1. An earthcompaction roller comprisinga-hollow body member adaptedto receive weight producing ballast and having a transversely extende' ing arched recess between its front and-reanends, an axially aligned 'series of; ;pneumat-icfitired wheels mounted in; ;sai;d;..recess;; to lstlnport t-he body member with its center of gravity substan tially over the wheels, and a draft beam extending longitudinally through the lower partof the body, centrally thereof, said draft beam traversing said arched recess between two of such wheels and rigidly connecting opposite wall portions of the recess. I r

2. An earth compaction roller comprising a unitary hollow body member adapted to receive weight producing ballast and having a transversely extending arched recess substantially midway its front and rear ends, two pair of pneumatic tired wheels mounted in said recess, one pair under each half portion thereof, to support the body member with its longitudinal center of gravity substantially over the wheels and so the entire weight of the body will be trans versely distributed to both pairs of wheels, a shaft in the recess mounting eachpair of said wheels, a fore-and-aft extending support for each shaft positioned between each pair of wheels with each support oscillatably mounted whereby the wheels of each pair have freedom for oscillating movementwith respect to its side of the body member and bearings for the fore-and-aft supports disposed at the lower ends of the arched recess, said supports maintaining the lower ends of the recess wall in parallelism.

3. An earth compaction roller comprising a unitary hollow body member forming a single frame and adapted to receive weight producing ballast, said body having a recess extending transversely thereunder, and across its entire width, four pneumatically tired wheels coaxially disposed in said recess, two under each side of the body member, said wheels being mounted in pairs, a shaft in the recess for mounting each pair of wheels, a fore-and-aft extending support in the recess for each shaft positioned between the wheels of each pair with the support 'oscillatably mounted and with its axis fixed with respect to the body member, whereby the wheels of each pair are free to oscillate about the axis of said supports, and a bearing beamdisposed at each lower end of the transverse recess and in which the fore-and-aft supports are mounted, the wheel supporting shafts being parallel with and equidistantly spaced from said bearing beams, the entire imposed load of the body member and its ballast being transmitted equally to the four wheels, the wheels being spaced from each other and with the spacing between each two adjacent wheels being equal whereby the load supporting tires will compact the earth in four equally spaced 6 paths and with equally distributed each path.

4. An earth compaction roller comprising a unitary hollow body member forming a single frame and adapted to receive weight producing ballast, said body having a recess extending transversely thereunder, and across its entire width, four pneumatically tired wheels coaxially disposed in said recess, two under each side of the body member, said wheels being mounted in pairs, a shaft in the recess for mounting each pair of wheels, a fore-and-aft extending support in the recess for each shaft positioned between the wheels of each pair with the support oscillatably mounted and with its axis fixed with respect to pressure on the body member, whereby the wheels of each pair are free to oscillate about the axis of said support, reinforcing means at the lower ends of the transverse recess and in which the support is mounted with the supports acting to maintain said lower ends in parallelism and in spaced relation, the entire imposed load of the body member and its ballast being transmitted equally to the four wheels, the wheels being spaced from each other and with the spacing between each two adjacent wheels being equal whereby the load supporting tires will compact the earth in four equally spaced paths and with equally distributed pressure on each path, and thespacing between the treads of each two adjacent tires being substantially less than the width of the tread of either of such tires whereby the compaction forces will not exert any substantial movement of earth material upwardly between the tires.

CHESTER W. BROS. ARCHIE 0-. WILLIAMSON. ULYSS O. GUIGNARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,256,594 Ingram -4" Sept. 23, 1941 2,295,645 Flynn Sept. 15, 1942 2,336,814 Suter Dec. 14, 1943 2,510,817 Greiner et al June 6, 1950 OTHER REFERENCES Engineering News-Record, June 11, 1936, page 835.

Roads and Streets, January 1948, pages 82, 83 and 84. 

